Security deposit for landscaping

[Gen Blaylock]

Hi All, first time posting and appreciate all the invaluable info over the years. Have a tenant that is moving out after 3 years. They take very good care of our end unit TH but have been the most needy of our 5 tenant properties in VA. Our lease states that tenants are responsible for yard maintenance. We had mature English ivy on the side and husband got severe reaction from poison ivy while working. I had recently been out to spray the exterior and did not see any poison ivy. They wanted us to remove and I referred to the lease and said to pull to eliminate or hire a professional. They removed all the english ivy and replaced it w a few hostas but mostly mulch which they never asked for in writing. I have verbally told them they can plant flowers and such in the mulch area in the backyard as I want them to enjoy the space. I informed them that they need to replace it to its original ground cover (low maintenance/absorbs rainwater which is a huge issue in our city) but they are refusing and have stated they expect all their security deposit returned. We are getting estimates and plan to withhold the cost from the deposit. While what they planted looks nice it will require us and future tenants more yard maintenance at a higher cost. Is it fair and would you withhold? TIA!